ChemInform Abstract: Strain Energy Effect on the Reactivity of Bridgehead Halides in Electron Transfer Reactions

Abstract

Abstract We here report MNDO and AM1 calculations for halobridgehead compounds which indicate that an increase in their angular strain is aoocmpanied by more negative reduction potentials as measured through their LUMO energies. The theoretically predicted reactivity agrees with that determined experimentally. The dissociative or non-dissociative nature of the electron capture reaction for the compounds is estimated through the localization of the corresponding radical anion intermediates as minimum of the potential surfaces. Our calculations indicate that for bridgehead chlorides, which lead to pyramidal radicals, the electron transfer is a non-dissociative step, while for t-butyl chloride, the process is dissociative leading to a planar t-butyl radical. The presence of a substituent that lowers the LUMO of the halobridgehead compounds increases their reactivity in ET reactions. This effect is explained through an orbital mixing of the molecular orbitals involved in the ET process.